Throttle Body Fuel Injection (“TBI”) is a type of Electronic Fuel Injection (“EFI”) for internal combustion engines that became main stream in factory vehicles during the 1980's. TBI Fuel Injection consists of an air metering valve that contains fuel injectors. The air metering valve allows more airflow as driver depresses gas pedal. The fuel injectors add fuel as a function of airflow. The TBI is controlled by an Electronic Control Unit (“ECU”).
Factory car producers moved away from this type of fuel injection as government emissions standards increased in the mid-to-late 1980's. However, the aftermarket automotive parts industry started selling aftermarket TBI fuel injection systems in the late 1980's. These systems were designed to replace the carburetor on older carbureted vehicles from the 1960's to 1980's.
One of the limitations of many aftermarket fuel injection systems is that the end consumer has to have a significant level of knowledge on tuning the ECU that controlled these systems. Recently, technology has advanced and several companies now offer systems that are “self-tuning”, where the end consumer only has to perform basic installation, and the ECU monitors various sensors and automatically tunes itself. This has caused resurgence in people purchasing TBI systems to retrofit older carbureted vehicles. The main benefit of TBI fuel injection is the fact that it can be retrofit fairly easy on older carbureted vehicles, on many different applications, as compared to other types of fuel injection methods such as Multiport EFI, which requires replacement of a multitude of original engine components.
Factory TBI system designs utilized fuel injectors that sprayed fuel at higher pressure that were placed vertically above the throttle plates of the throttle body. Mostly due to aesthetics, and available fuel injector designs, most aftermarket TBI systems place fuel injectors horizontally (or close to a horizontal position) into the sides of the throttle body. Unlike the factory TBI designs, this horizontal placement requires a throttle body design that redirects the normal fuel injector spray pattern. If fuel is not directed into the throttle body in a way that atomizes the fuel so it can thoroughly mix with the airstream through the throttle body, the engine may not run smoothly, may not make adequate power, and may have poor fuel economy and emissions.